The purposes of the proposed research are to explain drug use among youth by an application of utility theory, and examine the relevance of the findings for programs and policy designed to prevent drug abuse. Utility theory postulates that behavior is determined by the imbalance of benefits and costs people perceive to result from behavior, and that this is influenced by the individual's perception of the likelihood a benefit or cost would be realized if the behavior occurred, and the length of time between when behavior occurs and the benefits or costs would be accrued. Many research, program, and policy considerations of drug behavior include at least the implicit recognition of some aspect of utility theory, but no research has tested the theory as it might relate to drug behavior. Between four and five thousand North Carolinians will complete self-administered questionnaires when they are in the seventh grade, and again one and two years later. Analyses will be directed toward assessing (1) the relationship between utility and drug behavior: whether used, type of drug used, frequency of use and continuation, (2) those relationships when variables considered to be antecedent to utility are included in the analyses, (3) which combinations of perceived benefits and costs are most influential upon behavior; (4) the relative merits of considering the perceived benefits and costs together rather than as separate variables, (5) the influence of drug behavior upon utility, and (6) how changes in utility might produce changes in drug behavior. The findings will be considered in terms of their implications for programs and policy designed to influence drug behavior.